Abstract: Extremely high density neutrons could be produced in inertial confinement fusion, therefore the neutron-neutron collision process can no longer be neglected, especially that it leads to production of super-high energy neutrons of important value for diagnosis technique. For numerical simulation of neutron-neutron collision, Monte Carlo methods generally suffer from low efficiency, while deterministic methods have limited accuracy. In this paper, several measures are taken to improve the accuracy of deterministic method: Firstly, the phase space discretization of neutron transport calculation adopts discontinuous finite element method, and the numbers of angle discretization and the scattering order are relatively large; Secondly, direct Monte Carlo tallying method is used to obtain highly accurate multi-group cross sections; thirdly, a neutron-neutron collision source iteration method that converges to real solution is introduced. At last, numerical verification shows that the enhanced deterministic method has favorable stability and accuracy, the non-linear problem arise from consideration of neutron-neutron collision process can be solved with reliable accuracy.